The Distribution of Prepotency

Abstract

MR. GALTON has raised under this heading a most important point—or, rather, a series of most important points—in the problem of evolution. Perhaps I maybe permitted to say a few words with regard to his views on evolution by sports and by normal variation. Mr. Galton's opinion, I think, is that sports are inherited in a higher degree than improbable normal variations, and that evolution must accordingly take place very largely by means of the former. To use a term I have introduced elsewhere, the sport connotes a shifting of the focus of regression, but any normal variation, however improbable, does not. In the preface to the 1892 edition of his “Hereditary Genius,” Mr. Galton writes: “All true variations are (as I maintain) of this kind [i.e. sports], and it is in consequence impossible that the natural qualities of a race may be permanently changed through the action of selection upon mere variations. The selection of the most serviceable variations cannot even produce any great degree of artificial and temporary improvement, because an equilibrium between deviation and regression will soon be reached, whereby the best of the offspring will cease to be better than their own sires and dams.” And again: “The case is quite different in respect to what are technically known as ’sports.’ In these a new character suddenly makes its appearance in a particular individual, causing him to differ distinctly from his parents and from others of his race. Such new characters are also found to be transmitted to descendants. Here there has been a change of typical centre, a new point of departure has somehow come into existence towards which regression has henceforth to be measured, and consequently a real step forward has been made in the course of evolution. When natural selection favours a particular sport, it works effectively toward the formation of a new species, but the favour that it simultaneously shows to mere variations seems to be thrown away so far as that end is concerned.”